Dissection of the different entropic contributions for proteins is still incomplete due to the fact that most of the terms that contribute to it are strongly correlated to one another as well as to some enthalpic contributions. In a previous paper (Proteins25:146-156), we estimated the magnitude of backbone entropy associated with the folding-unfolding transition. Nevertheless, this contribution itself is not sufficient to predict accurately the unfolding endotherm for a globular protein. In our present calculations, the error of conformational entropy is less than 3% but such a difference could account for as much as q 10 C in the stability of an average globular protein. This project aims to dissect the effect of electrostatic charges to the backbone entropy. Several dipeptides containing different combinations of charges and distances in between them were generated using Quanta and their energies were calculated and minimized using fixed dihedrals in Xplor and the OPLS parameters. These backbone entropy values reflect a change that could account for some of the difference between the calculated and the experimental stability for globular proteins.